PCLPlotter — Point Cloud Library 0.0 documentation (original) (raw)
PCLPlotter provides a very straightforward and easy interface for plotting graphs. One can visualize all sort of important plots - from polynomial functions to histograms - inside the library without going to any other software (like MATLAB). Please go through the documentation when some specific concepts are introduced in this tutorial to know the exact method signatures.
The code for the visualization of a plot are usually as simple as the following snippet.
#include #include #include
#include<pcl/visualization/pcl_plotter.h> //...
int main () { //defining a plotter pcl::visualization::PCLPlotter * plotter = new PCLPlotter ();
//defining the polynomial function, y = x^2. Index of x^2 is 1, rest is 0 std::vector func1 (3,0); func1[2] = 1;
//adding the polynomial func1 to the plotter with [-10, 10] as the range in X axis and "y = x^2" as title plotter->addPlotData (func1, -10, 10, "y = x^2");
//display the plot, DONE! plotter->plot ();
return 0; }
If this program is compiled and run, you will get the following output
Basic code structure
The following snippet shows the basic structure of code for using PCLPlotter
... //1. define a plotter. Change the colorscheme if you want some different colorscheme in auto-coloring. pcl::visualization::PCLPlotter *plotter = new PCLPlotter ("My Plotter");
... //2. add data to be plotted using addPlotData* () functions plotter->addPlotData* ();
... //3. add some properties if required plotter->setWindowSize (900, 600); plotter->setYTitle ("this is my own function");
... //4. display the plot plotter->plot ()
All the subsequent sections will elaborate the above concept in detail.
Auto-coloring
You have the choice to add your own color to the plot in addPlotData*() functions. But if left empty, the plotter will auto-color depending upon a color-scheme. The default color-scheme is vtkColorSeries::SPECTRUM which contains 7 different (normal) hues over the entire spectrum. The other values are vtkColorSeries::WARM, vtkColorSeries::COOL, vtkColorSeries::BLUES, vtkColorSeries::WILD_FLOWER, vtkColorSeries::CITRUS. You can change the colorscheme by setColorScheme () function. To reflect the effect of the color-scheme to all the plots call this function before calling any addPlotData*() functions.
Different types of plot input
Have a look at the addPlotData() functions in the documentation for their detailed signatures. The prototypes pretty much tell about their functionalities. The following subsections contains some of the important input method of the plot.
Point-Correspondences
This the most fundamental way of providing input. Provide the point correspondences, that is (x,y) coordinates, for the plot using a std::vectorstd::pair in addPlotData
... std::vector<std::pair<double, double> > data; populateData (data); plotter->addPlotData (data,"cos"); ...
The other ways of input for point correspondences are two arrays of same length denoting the X and Y values of the correspondences.
Table
This is same as the previous one except the fact that the user stores the correspondences in a text file in the form of an space delimited table. This forms a substitute for the plotting using MS Excel. A very simple executable (without decoration) which performs the functionalities of MS Excel Plotter will be the following.
#include<pcl/visualization/pcl_plotter.h>
int main (int argc, char ** argv) { pcl::visualization::PCLPlotter * plotter = new PCLPlotter (); plotter->addPlotData (argv[1]); plotter->plot ();
return 0; }
Polynomial and Rational Functions
Polynomial are defined in terms of vector of coefficients and Rational functions are defined in terms of pair of polynomial (pair of numerator and denominator) . See the definition in the documentation. The following snippet plots the function y = 1/x
... std::vector func1 (1,0); func1[0] = 1; std::vector func2 (2,0); func1[1] = 1;
plotter->addPlotData (std::make_pair (func1, func2),-10, 10, "y = 1/x"); ...
A custom explicit function
User can specify a custom function, f depicting the relation: Y = f(X) in the form of a callback
... double identity (double val) { return val; } ...
... plotter->addPlotData (identity,-10, 10,"identity"); ...
Adding other properties and decorations
One can add other properties of the plot like title, legends, background colours etc. You can call these functions at any time before any display (plot()/spin*()) function call.
... plotter->setTitle ("My plot"); //global title plotter->setXTitle ("degrees"); plotter->setYTitle ("cos"); plotter->setShowLegend (true); //show legends ... plotter->plot (); ...
Other Functionalities
PCLPlotter provides few other important functionalities other than plotting given a well defined plots and correspondences. These includes a histogram plotting functions and all functionalities of the legacy class PCLHistogramVisualizer.
‘Plotting’ Histogram
PCLPlotter provides a very convenient MATLAB like histogram plotting function (hist() in MATLAB). It takes raw data and bins them according to their frequency and plot them as bar chart.
...
std::vector freqdata = generateNomalDistData ();
plotter->addHistogramData (freqdata,10); //number of bins are 10
plotter->plot (); ...
PCLHistogramVisualizer functions
All functionalities of PCLHistogramVisualizer has been rewritten and added to the plotter with their signature retained. See the documentation for method details.
Display
To display all the plots added use the simple function - plot(). PCLPlotter is also provided with the legacy spin*() functions which can be used for animations or updating the plots with time. The following snippet shows the functionality.
...
//data and callback defined here ...
plotter->addPlotData (func1, -10, 10, "y = x^2"); plotter->spinOnce (2000); //display the plot for 2 seconds
plotter->clearPlots (); plotter->addPlotData (identity,-10, 10,"identity"); plotter->spinOnce (2000);
plotter->clearPlots (); plotter->addPlotData (abs,-5, 5,"abs"); plotter->spinOnce (2000); ...
Demo
Following is a complete example depicting many usage of the Plotter. Copy it into a file named pcl_plotter_demo.cpp.
1/* \author Kripasindhu Sarkar */
2
3#include<pcl/visualization/pcl_plotter.h>
4
5#include
6#include
7#include
8#include //for std::abs()
9
10using namespace pcl::visualization;
11
12void
13generateData (double *ax, double *acos, double *asin, int numPoints)
14{
15 double inc = 7.5 / (numPoints - 1);
16 for (int i = 0; i < numPoints; ++i)
17 {
18 ax[i] = i*inc;
19 acos[i] = std::cos (i * inc);
20 asin[i] = sin (i * inc);
21 }
22}
23
24//.....................callback functions defining Y= f(X)....................
25double
26step (double val)
27{
28 if (val > 0)
29 return (double) (int) val;
30 else
31 return (double) ((int) val - 1);
32}
33
34double
35identity (double val)
36{
37 return val;
38}
39//............................................................................
40
41int
42main ()
43{
44 //defining a plotter
45 PCLPlotter *plotter = new PCLPlotter ("My Plotter");
46
47 //setting some properties
48 plotter->setShowLegend (true);
49
50 //generating point correspondences
51 int numPoints = 69;
52 double ax[100], acos[100], asin[100];
53 generateData (ax, acos, asin, numPoints);
54
55 //adding plot data
56 plotter->addPlotData (ax, acos, numPoints, "cos");
57 plotter->addPlotData (ax, asin, numPoints, "sin");
58
59 //display for 2 seconds
60 plotter->spinOnce (3000);
61 plotter->clearPlots ();
62
63
64 //...................plotting implicit functions and custom callbacks....................
65
66 //make a fixed axis
67 plotter->setYRange (-10, 10);
68
69 //defining polynomials
70 std::vector func1 (1, 0);
71 func1[0] = 1; //y = 1
72 std::vector func2 (3, 0);
73 func2[2] = 1; //y = x^2
74
75 plotter->addPlotData (std::make_pair (func1, func2), -10, 10, "y = 1/x^2", 100, vtkChart::POINTS);
76 plotter->spinOnce (2000);
77
78 plotter->addPlotData (func2, -10, 10, "y = x^2");
79 plotter->spinOnce (2000);
80
81 //callbacks
82 plotter->addPlotData (identity, -10, 10, "identity");
83 plotter->spinOnce (2000);
84
85 plotter->addPlotData (std::abs, -10, 10, "abs");
86 plotter->spinOnce (2000);
87
88 plotter->addPlotData (step, -10, 10, "step", 100, vtkChart::POINTS);
89 plotter->spinOnce (2000);
90
91 plotter->clearPlots ();
92
93 //........................A simple animation..............................
94 std::vector fsq (3, 0);
95 fsq[2] = -100; //y = x^2
96 while (!plotter->wasStopped ())
97 {
98 if (fsq[2] == 100) fsq[2] = -100;
99 fsq[2]++;
100 char str[50];
101 sprintf (str, "y = %dx^2", (int) fsq[2]);
102 plotter->addPlotData (fsq, -10, 10, str);
103
104 plotter->spinOnce (100);
105 plotter->clearPlots ();
106 }
107
108 return 1;
109}
Compiling and running the program
Add the following lines to your CMakeLists.txt file:
1cmake_minimum_required(VERSION 3.5 FATAL_ERROR) 2project(pcl_plotter) 3find_package(PCL 1.7 REQUIRED COMPONENTS common visualization) 4add_executable(pcl_plotter pcl_plotter_demo.cpp) 5target_link_libraries(pcl_plotter ${PCL_LIBRARIES})
Compile and run the code by the following commands
$ cmake . $ make $ ./pcl_plotter_demo
Video
The following video shows the the output of the demo.